1. Field of the Invention
The present invention relates to an intrabody introduced device, and more particularly to detecting a supply voltage of a battery for the intrabody introduced device.
2. Description of the Related Art
In recent years, a capsule type endoscope has emerged as one of the intrabody introduced devices in the endoscope area. The capsule type endoscope has an imaging function and a wireless function. The capsule type endoscope is swallowed by a test subject as a test body for observation (examination) and then moves inside the stomach, the small intestine, or other organs (in the body cavity) with the organs' peristaltic motion for the observation period until it is excreted naturally from the test subject. The capsule type endoscope takes images of the inside of the organs sequentially by using the imaging function while it moves inside the organs.
Image data captured in the body cavity by the capsule type endoscope during the observation of the organs while moving inside thereof is transmitted to an external device provided outside the test body by using a wireless function (radio communication or the like) and then stored in a memory provided inside the external device. The test subject carries the external device, whereby the test subject is not restrained in behavior during the observation period until the capsule type endoscope is excreted after the test subject swallows the capsule type endoscope. After the observation, images of the inside of the body cavity are displayed on a screen of a display or the like on the basis of the image data stored in the memory of the external device, whereby a doctor or a nurse can make a diagnosis.
In this type of capsule type endoscope, there is a swallowable capsule type endoscope such as, for example, one disclosed in the brochure of International Publication No. 01/35813. This brochure suggests a capsule type endoscope provided inside with a reed switch turned on or off according to an external magnetic field and an arrangement in which the capsule type endoscope is contained in a package including a permanent magnet for supplying the external magnetic field in order to control driving of the capsule type endoscope. More specifically, the reed switch in the capsule type endoscope maintains the OFF state in an environment with a magnetic field of a certain or higher intensity, while it is turned on by a decrease in the intensity of the external magnetic field. Therefore, the capsule type endoscope is not driven in a condition where it is contained in the package. When the capsule type endoscope is taken out of the package for swallowing, the capsule type endoscope is separated from the permanent magnet and is not influenced any more by the magnetic force and thus starts to be driven. With this arrangement, it is possible to prevent the capsule type endoscope from being driven in the condition where it is contained in the package. After the capsule type endoscope is taken out of the package, it is driven and therefore takes images using the lighting function and the imaging function and transmits image signals using the wireless function.
The capsule type endoscope drives a function executing section for executing predetermined given functions such as a lighting function, an imaging function, and a wireless function by supplying power from a battery such as, for example, a button dry cell. Therefore, if the battery is used for a long period of time, the supply voltage of the battery decreases to a medium potential and the medium potential may cause latch-up or some other phenomenon in the load side of the function executing section, whereby the capsule type endoscope may enter a failure mode. To prevent such a phenomenon, the circuit can be configured so that the battery is disconnected from the function executing section in the medium potential. Current, however, is consumed also in a circuit for detecting the supply voltage of the battery. The prior art does not disclose or suggest reducing the power consumption of the circuit for detecting the supply voltage of the battery to increase the battery life.
This invention has made in view of the above problems, and has its object in providing an intrabody introduced device capable of reducing consumption of electric current used for detecting the current voltage of an electric source like a dry cell.